This invention relates to a disk polisher for grinding and/or polishing disk-shaped workpieces, and more particularly to a component of such a disk polisher which comes into contact with the workpieces and from which polished or ground workpieces can be removed easily and dependably.
In the fabrication of disk-shaped objects such as memory disks, silicon wafers and optical mirrors (hereinafter generally referred to as workpieces), use is frequently made of an apparatus, herein broadly referred to as a disk polisher, having a horizontal turntable and a holder plate thereover. The workpieces to be polished or ground may be placed in indentations created on the top surface of a tray-like carrier as disclosed, for example, in U.S. Pat. Application Ser. No. 471,830, filed Jan. 29, 1990 and assigned to the present assignee, and the loaded carrier is placed on top of the turntable and rotated together therewith such that the workpieces undergo generally horizontal rotary motions. Pieces of grinding stone are attached to the holder plate above the turntable such that their flat grinding surfaces are not only horizontal but mutually coplanar, facing vertically downward. With the loaded carrier and the grinding stone pieces thus set, an abrasive is applied with water on the surfaces of the workpieces to be ground and the holder plate is lowered as the turntable is caused to rotate such that the top surfaces of the workpieces are ground by moving against the grinding stone surfaces.
When the holder plate is lifted after such an operation, however, the workpieces tend to remain stuck to the holder plate and be lifted therewith due to the surface tension of water used with the abrasive. This makes it difficult to unload the processed workpieces by an automatic means such as a robot gripper and the workpieces may be damaged if they drop after being lifted from the carrier surface.
When a disk polisher of this type is used for polishing disk-shaped workpieces instead of for grinding, a piece of polishing cloth may be attached to the holder plate instead of the pieces of grinding stone. In such a situation, too, it has been desirable to eliminate the problem of workpieces adhering to the holder plate when the holder plate is lifted after the workpieces are polished.